1. Field of the Invention
The present invention relates to articulators for the dental art, used for carrying out dental prosthesis and occlusal analysis work.
These apparatus, while serving as supports for lower and upper jaw moldings, allow the mandibular movements to be reproduced.
2. Description of the Prior Art
The articulators usually used comprise a lower platen whose front part supports an incisive table, and whose rear part comprises vertical legs supporting two condylar balls forming ball joints to which an upper member is hinged. The upper member comprises a rear hub having appropriate housings for housing the condylar balls and forming an articulation. A lower platen, integral with the hub, receives in its front part an incisive rod coming to bear on the incisive table for positioning the upper member with respect to the lower platen.
For reproducing the movements of the jaw, the housings of the hub are usually limited by a flat upper guide ramp slanting towards the front by an angle reproducing the condylar slope; a lateral outer ramp, or BENNETT's wing, open towards the front by an angle reproducing BENNETT's angle, limits the movement of the ball outwardly; a rear wall limits the movements of the ball rearwardly while allowing transverse movements. The lower and upper jaw moldings are fitted to the device by means of mounting plates fixed to the central part of the lower platen and of the upper platen.
French Pat. No. 2 431855 describes such an articulator in which provision is further made for making BENNETT's wings adjustable by lateral translation with respect to the housing of the hub; bringing the two BENNETT's wings closer together, in relation with a constant spacing of the condylar balls, provides a play which allows the movement called immediate lateral displacement, to be reproduced, that is to say a transverse translation of the upper member with respect to the lower member, the condylar balls remaining in contact with the rear wall, before reproducing a BENNETT movement by sliding of a ball against the corresponding BENNETT's wing.
In this document are also described means for selectively locking the hub in centered relation. By selective locking in centered relation is meant a function, according to which the user, after choosing an immediate lateral displacement of a given value, may instantaneously prevent the transverse translation momentarily so as to reproduce a pure centered rotational movement of the upper member with respect to the lower member, and may then instantaneously again allow the transverse translation without having to adjust its value a second time. The means described in this document comprise a rod integral with an intermediate cross piece of the lower member, and coming to bear selectively in a circular peripheral groove provided in the hub. The articulator described thus comprises means for allowing an immediate lateral displacement of the lower member and means for selectively obtaining locking thereof in centered relation.
However, such an arrangement leads to the construction of expensive articulators, for reproduction of the immediate lateral displacement movement requires the use of relatively complex housings. The number of precision machined parts is relatively high, which leads to a high cost. The intermediate cross-piece or the rod which is associated therewith prevents or considerably hinders access to the prothesis through the rear of the apparatus. The adjustments require the handling of several parts: BENNETT's wings for choosing the amplitude of translation, and the rod for locking or unlocking.
Patent NL-A-80 06043 describes an articulation in which the condylar balls are integral with the upper member and engage in housings integral with the lower member. The condylar balls have an adjustable spacing. For that, they are each mounted on half shafts sliding in the upper member, held apart by a spring and actuated by superimposed sliding plates. This device allows the immediate lateral displacement to be adjusted, but the pure centered rotation can only be obtained by moving the two sliding plates and thus losing the information about the preceding lateral displacement value. The device does not allow selective locking in centered relation.
The object of the present invention is in particular to overcome the drawbacks of the known devices by proposing an articulator allowing the immediate lateral displacement to be adjusted in simple way with selective locking in centered relation by operating a single member.
Another object of the present invention is to provide articulators whose centered relation blocking devices are particularly simple, easy and rapid to use, do not hinder access through the rear of the articulator and lead to using a minimum of precision machined parts.
Another object of the invention is to propose an articulator in which the amplitude of the immediate lateral displacement movement is chosen equal to a predetermined value, corresponding to the majority of cases met with in the usual human morphologies; the same articulator may further reproduce two immediate lateral displacement amplitudes, covering the majority of morphological cases for different ages.
Another object of the invention is to propose an articulator in which the centered relation locking device may be associated with a device for the immediate pinning of the upper member on the lower member and the immediate unpinning thereof without manipulating levers or other accessories. The articulator thus designed is very easy to use because the preset values of immediate lateral displacement, of BENNETT's angle and of condylar slope reduce considerably the settings required for using the apparatus.
The preset values thus defined, identical for all the apparatus of the same series, allow the user to use several articulators successively and equally well for working the same prosthesis.